Depends on the age of the kids.... but if they're old enough - what about the best en papillote dish they can prepare? Its a lovely way of cooking, the best part being when you open it and the aromas come out. Or the best bbqed kebab - could be meat, fish, fruit, veg, any combination - they'll need to blanch some of the hard veg first to get them to cook at same time as meat, marinate some meats if they like, etc etc... have fun and let us know how it goes
DC
P.S. Give us the recipe if they come up with a real goodie hehehe